Internal combustion engine structure

ABSTRACT

The disclosure illustrates an opposed multicylinder internal combustion engine suitable for aircraft use. The engine is fabricated from a pair of matched crankcase halves which enable die casting for limited production. The matched crankcase halves and rows of cylinder barrels and cylinder heads on opposed sides are secured by bolts which extend the width of the engine. The crankcase halves are mounted together at a series of ribs symmetrically positioned with respect to the midpoint of the crankcase halves. The cylinder barrels are mounted on pads offset from the midpoint so that the opposed barrels are in a staggered relationship on the assembled engine.

l nited States Patent 2,969,781 1/1961 Kolbe ,Assignee Inventors Richard II. Syson Cogan Station, Pa.;

John W. Eckert, King, Ontario, Canada 767,780

Oct. 15, 1968 Mar. 9, 1971 Arco Corporation Williamsport, Pa.

Appl. No. Filed Patented INTERNAL COMBUSTION ENGINE STRUCTURE 8 Claims, 6 Drawing Figs.

US. Cl. l23/56(A), 123/195, 123/196 Int. Cl ..F02b 75/24, F02f 7/00, FOlm 11/02 Field of Search 123/56 (A), 1, 56 (8)1, 56 (A),56 (B), 195, 196

References Cited UNITED STATES PATENTS 2,764,143 9/1956 Wiseman 123/195 3,023,847 3/1962 Kolbe l23/196X 3,123,058 3/1964 Wooge 123/195X Primary Examiner-Wendell E. Burns Attameys-Charles M. Hogan and Gary M. Gron ABSTRACT: The disclosure illustrates an opposed multicylinder internal combustion engine suitable for aircraft use. The engine is fabricated from a pair of matched crankcase halves which enable die casting for limited production. The matched crankcase halves and rows of cylinder barrels and cylinder heads on opposed sides are secured by bolts which extend the width of the engine. The crankcase halves are mounted together at a series of ribs symmetrically positioned with respect to the midpoint of the crankcase halves. The cylinderbarrels are mounted on pads offset from the midpoint so that the opposed barrels are in a staggered relationship on the assembled engine.

PATENTEU MAR 9197: 3,568,649

sum 1 or a RICHARD H. SYSON BY JOHN W. ECKERT H1 m M h. 2:: l-

Z I'ORNEYS.

REFERENCE PLANE A PATENTEUHAR 9|97| assasde SHEEI 2 BF 4 INVENTORS. RICHARD H. SYSON JOHN W. ECKERT fi ATTORNEYS.

PATENTEU "AR 9 I971 SHEET 3 BF 4 ATTORNEYS.

PATENIED MAR 9191: 3,5 49

SHEET m or a REFERENCE PLANE B INVENTORS. RICHARD H. SYSON BY JOHN W. ECKERT ATTORNEYS.

INTERNAL QOMBUSTIGN ENGINE STRUCTURE The present invention relates to internal combustion engines and more particularly to their type of construction.

The opposed-cylinder, air-cooled internal combustion engine has long been used for light aircraft propulsion, owing to its light weight and minimum frontal area. The extended use of this type of engine has achieved a high level of reliable operation and efficient manufacture.

However, one of the problems in manufacturing this type of engine is the fact that certain parts must be cast, owing to their complex shape. One such component is the crankcase assembly which provides a housing for the engine crankshaft, a base for mounting the engine in a vehicle, and a support for the engine cylinders and other accessories. According to present practice the engine crankcase is practice the engine crankcase is formed from two separate halves, a right half and a left half. There are several reasons for this. The opposed cylinders must be arranged in a staggered fashion to enable connection with the engine crankshaft; the crankcases have an output shaft on the front and an accessory gearbox on the back; and the engine is mounted in a vehicle with a four-point arrangement. The right and left crankcase halves generally are manufactured by sand casting from aluminum alloy. Since the cylinders, the crankshaft and the crankcase halves must be accurately positioned and fitted together, the crankcase halves must be extensively machined. This machining process is quite extensive because the inherent wide tolerances in a sand-casting process necessitate oversize castings. This machining not only generates a 'lot of waste material but also represents greatly increased labor costs. 1

It would be desirable to reduce these costs by die casting which enables a precise control of dimensions, thereby reducing the waste material by minimizing the required machining operations. However, the normal production volume of aircraft engines is not sufficiently great to justify the investment in two dies to form the crankcase halves.

Accordingly, it is an object of the present invention to provide a simplified engine crankcase structure which will enable the use of economical manufacturing procedures for limited volume production.

The above ends are achieved in one aspect of the invention by providing a crankcase assembly for an internal combustion engine having a row of generally opposed cylinders extending from the crankcase assembly. The crankcase assembly comprises a pair of matched elongated casings having an opposed opened inner side and an outer facing side. A means is provided on the opposed open side of the casings for securing the casings to one another, the securing means being symmetrical about a normal plane at the midpoint of the longitudinal axis of the casing. Means are provided on the outer facing side of the casing for mounting the row of cylinders, the cylinder mounting means being offset relative to the normal plane so that when the casings are secured to one another the opposed cylinder will be mountable thereon in staggered relationship.

The above and other related objects and features of the present invention will be apparent from a reading of the description of the disclosure shown in the accompanying drawings and the novelty thereof pointed out in the appended claims.

In the drawings:

FIG. 1 is a detailed plan view of an opposed multicylinder engine having a crankcase assembly embodying the present invention; I

FIG. 2 is a view taken on line 2-2 of FIG. 1, showing particularly the inner side of a crankcase half used in the crankcase assembly of FIG. I;

FIG. 3 is a view taken on line 3-3 of FIG. 1, showing particularly the outer side of a crankcase half used in the crankcase assembly of FIG. ll;

FIG. 4* is a view taken on line 4-4 of FIG. 1;

FIG. 5 is a view taken on line 5-5 of FIG. 2, showing particularly the bottom portion of the crankcase assembly of FIG.

' FIG. 6 is a cross-sectional view of the crankcase half shown in FIG. 2 and taken on line 6-6.

Referring particularly to FIG. ll, there is shown a plan view of an engine It), showing in simplified fashion its major external components. The engine comprises a pair of generally longitudinal crankcase halves 12 forming supports for rows of horizontally opposed cylinder barrels l4 and 16, respectively. The cylinder barrels have cylinder head assemblies 18 and 20, respectively, at their outer extremities. The cylinder head assemblies 18, 20, cylinder barrels 14, 16 and crankcase halves 12 are held together by bolt assemblies 15 as later described in detail.

The cylinder barrels 14, 16 are bored and have piston assemblies (not shown) displaceable therein in response to ignition of successive charges of a combustible fuel-air mixture in the head assemblies 18. The reciprocating motion of the piston assemblies is translated into rotary motion by connecting rods (not shown) extending to an engine crankshaft 22 (shown in FIG. 2), journaled in crankcase halves 12.

The forward end of the crankshaft 22 is splined at 24 (FIG. 2) to connect with a suitable gear train (not shown) in the forward portion of the crankcase halves 12. This gear train is used to drive cam drive assemblies 26 and 28, respectively. These assemblies are connected to overhead camshafts (not shown) positioned in the head assemblies 18, 20 to reciprocate valves which provide intake and exhaust of unburned and burned mixture.

The engine 10 provides a primary power output through the forward end of the crankshaft 22 which connects to a gear train in an output gear box 30. For aviation purposes, the output gear box 30 is connected to a propeller. The crankshaft 22 additively has a flange 32 (FIG. 2) at the aft end of the crankshaft 22 which connects to a suitable gear train positioned in an accessory gear box 34 mounted to the aft end of the crankcase halves 12. The gear train in the accessory gear box is used to drive the various accessories of the engine, e.g., magnetos, generators, etc.

The engine has a lubricating system comprising an oil pump (not shown) which receives oil from a sump chamber 36 (shown in FIGS. 2 and 3) mounted to the bottom side of the crankcase halves 12. The pump pressurizes the oil for delivery via a combination pressure valve and filter assembly 38 to the various portions of the engine which require lubrication. From there the fluid passes through an oil cooler assembly 40 mounted to the opposite side of the engine crankcase to the sump chamber 36.

In the above discussion only the external engine components have been shown to enable a sharper focus on the present invention. It should be apparent that with the teachings of the present invention, as described in detail below, particular gear trains, connecting rods, pistons and head assemblies may be adapted to the engine by those skilled in the art.

Attention is now directed to FIGS. 2-5 which show in detail one of the crankcase halves 12. In accordance with the present invention the crankcase halves 12 are identical and matched so that the same crankcase half may be used for either side. Referring particularly to FIGS. 2 and 3, each crankcase half 12 comprises a housing 50 having an outer facing side 52 (shown in FIG. 3) and an inner open side 54 (shown in FIG. 2). The housing 50 has a plurality of ribs 56 extending inwardly from its inner open side 54. The ribs 56 are positioned symmetrically with respect to a normal reference plane A extending through the longitudinal midpoint of the housing 50. Top and bottom bolt holes 55 extend through ribs 56 normal to the longitudinal axis of the housing 50. The housing 50 additionally has a longitudinal mating surface 58 along its upper side. The mating surface 58 has holes 60 symmetrically positioned with respect to the reference plane A and adapted to receive boltassemblies 62 (shown in FIG. 1). The housing 50 has identical end walls 64 having normal bolt holes en formed therethrough and positioned symmetrically with respect to reference plane A.

Referring now to FIG. 3, the outer side 52 of the housing 50 has a plurality of openings 68 surrounded by mounting pads '70 which receive the inner ends of the cylinder barrels 14. As

shown in FIG. 3, the cylinder barrel mounting pads 70 are offset with respect to the reference plane A. In fact, the mounting pads 70 are positioned so that the bolt holes 55 which extend through adjacent ribs 56 on the inner side 54 of the housing 50 also extend through fore and aft ends of the cylinder barrel mounting pads 70.

The outer side 52 of the housing 50 also comprises mounting pads 72 which are used to mount one of the cam drive assemblies 26 or 28 or the pressure valve filter assembly 38 or the oil cooler 40. Threaded bores 74 in the pads 72 receive suitable bolts which hold the selected assembly on the pad. It should be noted that the mounting pads 72 and threaded bores 74 are offset with respect to the reference plane A as are the cylinder mounting pads 70. However, the mounting pads 72 are symmetrical with respect to the row of cylinder mounting pads 70.

To support the engine in an aircraft or other vehicle a pair of engine mounting pads 76 are provided on the outer side 52 of the housing 50. The engine mounting pads 76 have threaded bores 78 to receive suitable mounting bolts. The engine mounting pads 76 are symmetrical with respect to the reference plane A.

The oil sump chamber 36 is mounted to the bottom side of the crankcase halves 12. For this purpose the housing 50 has an open bottom side provided with a longitudinal oil sump mounting pad 80. The oil sump mounting pad 80 has threaded bores 82 positioned symmetrically with respect to reference plane A. The threaded bores 82 receive bolts 84 that secure a flange 86 of the oil sump chamber 36 to the mounting pad 80.

' The engine crankcase halves 12 also provide endwise mounting for the output gear box 30 and the accessory gear box 34. For this purpose the end walls 64 of the housing 50 are provided with gear box mounting pads 88, as shown in FIG. 4. The gear box mounting pads 88 at the ends of the housing 50 have threaded bores 90 positioned symmetrically with respect to a reference plane B extending through the junction between the crankcase halves 12. In the manner the threaded bores 90 of one crankcase half are a mirror of the threaded bores 90 on the opposite gear box mounting pad 88 when the crankcase halves 12 are mounted together. The threaded bores 90 are adapted to receive studs 92. Nuts 93 are threaded on studs 92 to hold either the output gear box 30 or the accessory gear box 34 to the ends of the crankcase halves 12.

As stated previously, the crankcase halves 12 have a crankshaft 22 journaled therein. The crankshaft 22 has journals 96 which are received in arcuate recesses 94 at the inner side of the ribs 56, as shown in FIG. 6. The arcuate recesses in these ribs cooperate when the crankcase halves 12 are secured to one another to form a series of circular openings in which the journals 96 are received, as shown particularly in FIG. 5. It should be noted that the circular openings which receive the journals 96 are on adjacent sides of crankshaft throws 106. The axial midpoints ofthe throws 106 line up with the cylinder barrel centerlines shown in FIG. 5.

In order to provide a flow path for lubricating fluid from the oil lubricating system to the crankshaft journals 96, a series of coaxial holes 98 are drilled through the bottom portion 100 of the ribs 56. A longitudinal tube 102 having a coefficient of expansion equal to that of the crankcase half material, is extended through the openings 98 along the length of the housing 50. Generally the crankcase halves would be made of aluminum alloys and the tube 102 would be formed from identical material. Radial passageways 104 are then drilled from the arcuate recesses 94 in the ribs 56 through the walls of the tube 102 to its interior. When the tube is manufactured from aluminum, any burrs that remain from the drilling process may be easily removed by reaming the bore of the tube 102. The appropriate ends of the tubes 102 may be sealed off to provide a proper circulation of lubricating fluid from the oil cooler to the journals 96.

When the engine is assembled the crankcase halves 12 are secured together along the end walls 64 and upper surface 58 but primarily through the ribs 56. Because the ribs 56 are positioned symmetrically with respect to the reference plane A, each rib lines up with a corresponding rib on the opposite crankcase half 12, as shown particularly in FIG. 5. The cylinder barrels 14 then mount on the cylinder mounting pads 70 on the outer side of the housing 12. The cylinder mounting pads 70 are offset with respect to the reference plane A so that the cylinder barrels 14 extend from the outer sides 52 of the housing 50 in a staggered relationship, as shown in FIG. 5.

It should be noted that the ribs 56 are positioned so that the rib in line with the aft end of the cylinder mounting pad 70 on one side lines up with a rib extending to the forward end of a cylinder mounting pad 70 on the opposite side. In this way the ribs 56 may be used to support the journals 96 on each side of the crankshaft throws 106 to provide a highly stable support for the crankshaft 22.

Since the bolt holes 55 extend through ribs 56 and mounting pads 70, a single bolt assembly may be used to secure the opposing cylinder barrels and their crankcase halves together. The bolt assemblies 15 may terminate at flanges surrounding the base of the cylinder barrels, according to present practice. However, it is preferable to have the bolt assemblies 15 extend from the head assemblies 18 on one bank of the engine to the head assemblies 20 on the opposite bank of the engine. Particularly, the bolt assemblies 15 extend from the aft end of a head assembly on one bank of the engine to the forward end of the head assembly on the opposite bank of the engines. For the cylinders at the extreme ends of the banks or rows of cylinders, shorter bolt assemblies 110 are used and these bolt assemblies 110 terminate at the outer side of the opposite crankcase half 12.

It should be noted that the bolt assemblies 15 and 110 have expanded portions 17 and 111, respectively, adjacent the juncture between the crankcase halves 12. The expanded portions act in the passageways 55 to key the crankcase halves 12 together.

In this manner the cylinder barrels 14, 16 are secured to the crankcase halves through the cylinder heads 18, 20, thus placing the cylinder barrels in compression. Therefore, the cylinder pressure gas loads are taken in compression rather than tension, as in the case of a flange mounting. This greatly minimizes the stress on the cylinder barrels and enables the use of aluminum alloy construction rather than the present steel construction.

The camshaft drive housings 28 and 26 are mounted to the crankcase halves 12 in a staggered relationship since they mechanically connect with the head assemblies 18 and 20. The pressure valve and filter assemblies 38 and the oil cooler assembly 40 are mounted on the unused mounting pads 72 to eliminate the need for closure plates.

The provision of matched crankcase halves provides significant advantages from the standpoint of the engines manufacturing cost. The most important effect of matched crankcase halves is that the number of individual crankcase halves for a given engine is doubled. In most cases this economically justifies the use of a diecasting process to form them. The die casting of the crankcase halves provides a lower unit cost, closer control of tolerances and minimizes the necessary machining and resultant waste material. In addition, the die used to cast the crankcase halves may be provided with add-on center sections to form crankcase halves which will accommodate more or less cylinders, thereby enabling a single die to be used for a whole series of engines.

The use of the matched crankcase halves also enables a high degree of flexibility for the engine 10 because the gear box mounting pads 88 at either end of the crankcase halves identical. The primary power for the engine may be taken from either or both ends to meet the requirements of a vehicle being powered by the engine. In addition, the symmetrical positioning of the engine mounting pads 76 enables a relative- Iy rigid four-point mounting of the engine to an airframe or other vehicle which transfers more evenly the forces produced on the vehicle by the engine 10.

While a preferred embodiment of the present invention has been described, modifications will occur to those skilled in the art that do not depart from the spirit of the present invention. Accordingly, its scope is to be determined solely by the appended claims.

We claim:

l. A crankcase assembly for an internal combustion engine having a row of generally opposed-cylinders extending from said crankcase assembly and having an output gear box at one end and an accessory gear box at'the opposite end of said crankcase assembly, said crankcase assembly comprising:

a pair of matched elongated housings having an opposed open inner side and an outer facing side;

means on the opposed open side of said housings for securing said housings to one another, said securing means beingsymmetrical about a normal plane at the midpoint of the longitudinal axis of said housing; means on the outer facing side of said housing for mounting said row of cylinders, said cylinder mounting means being offset relative to said normal plane so that when said housings are secured to one another said opposed cylinders are mountable thereon in staggered relationship; end walls for said housings extending from said inner side and terminating in a plane extending through the longitu dinal juncture between said housings; and

means positioned on said end walls for mounting said output and accessory gear box, said mounting means on either end being equidistant from said longitudinal plane so that said accessory gear box and said. output gear box are adapted to be interchangeably mounted on the end walls of said housings.

2. A crankcase assembly as in claim 1 wherein said crankcase provides a housing for a crankshaft journaled therein and having throws in line with the midpoint of each of said cylinder mounting means, and wherein said housing securing means include:

a plurality of ribs extending from the inner side of said housings toward said opposed inner-side, said ribs having an arcuate recess therein for joumaling one side of said.

crankshaft; and

said ribs being positioned symmetrical about said normal plane and positioned in line withboth ends of said cylinder mounting means so that when the housings are secured to one another the ribs extending from said inner sides cooperate to journal said crankshaft in between said throws.

3. A crankcase assembly as in claim 1 for use with an engine including an oil sump chamber and wherein:

said housings have an open bottom side for receiving said oil sump; and

said crankcase assembly further comprises means on the bottom side of said housings for mounting said oil sump casing, said mounting means being positioned symmetrical about said normal plane. 4. A-crankcase assembly as in claim 1 wherein said crankcase assembly is adapted to provide a support for said engine, 5 and wherein said crankcase assembly further comprises:

mounting pads positioned adjacent opposite ends of said matched housings on the outer facing sides thereof for securing said engine to a support member; and said mounting means being symmetrical relative to said normal plane.

5. A crankcase assembly as in claim 1 wherein said housing securing means and said cylinder mounting means further includes:

passageway means extending through said housings normal to the longitudinal axis thereof and positioned so that a single passageway means extends through said casings adjacent one side of a cylinder on one casing and the other side of a cylinder on the opposite casing; and

bolt means extending through said passageway means for connecting said rows of cylinders to said casings and connecting said casings to oneanother. 6. A crankcase assembly as n claim 5 in combination with rows of cylinder assemblies extending from said cylinder mounting means, said cylinder assemblies having intermediate 25 barrel portions and head portions at the outer extremities thereof, and wherein:

said bolt means extends through the housings to an outer facing side of the head portion of a cylinder assembly on the opposite side of the engine axis; and whereby said housings and said cylinder barrels are secured in compression. 7. Apparatus as in claim 6 wherein:

said bolt means further comprise an expanded portion at the midpoint thereof to line up opposing passageway means through which the bolt means extends; and

whereby said bolt means key said crankcase halves with one another.

8. A crankcase as in claim 2 wherein said crankcase assembly further comprises means for providing a flow path for lubricating fluid to said joumaling means, said flow path means comprising:

a tube extending through openings in the plurality of ribs,

said tube being positioned generally parallel to the longitudinal axis of said housings and to one side of said arcuate recesses;

passageway means extending from the arcuate recess of said inner ribs through said inner ribs to the interior of said tubular member, said tubular member having apertures communicating with each of said passageway means; and

said tubular member having the same coefficient of expansion as said casings for preventing leaks of the junction therebetween over substantial temperature changes. 

1. A crankcase assembly for an internal combustion engine having a row of generally opposed cylinders extending from said crankcase assembly and having an output gear box at one end and an accessory gear box at the opposite end of said crankcase assembly, said crankcase assembly comprising: a pair of matched elongated housings having an opposed open inner side and an outer facing side; means on the opposed open side of said housings for securing said housings to one another, said securing means being symmetrical about a normal plane at the midpoint of the longitudinal axis of said housing; means on the outer facing side of said housing for mounting said row of cylinders, said cylinder mounting means being offset relative to said normal plane so that when said housings are secured to one another said opposed cylinders are mountable thereon in staggered relationship; end walls for said housings extending from said inner side and terminating in a plane extending through the longitudinal juncture between said housings; and means positioned on said end walls for mounting said output and accessory gear box, said mounting means on either end being equidistant from said longitudinal plane so that said accessory gear box and said output gear box are adapted to be interchangeably mounted on the end walls of said housings.
 2. A crankcase assembly as in claim 1 wherein said crankcase provides a housing for a crankshaft journaled therein and having throws in line with the midpoint of each of said cylinder mounting means, and wherein said housing securing means include: a plurality of ribs extending from the inner side of said housings toward said opposed inner sidE, said ribs having an arcuate recess therein for journaling one side of said crankshaft; and said ribs being positioned symmetrical about said normal plane and positioned in line with both ends of said cylinder mounting means so that when the housings are secured to one another the ribs extending from said inner sides cooperate to journal said crankshaft in between said throws.
 3. A crankcase assembly as in claim 1 for use with an engine including an oil sump chamber and wherein: said housings have an open bottom side for receiving said oil sump; and said crankcase assembly further comprises means on the bottom side of said housings for mounting said oil sump casing, said mounting means being positioned symmetrical about said normal plane.
 4. A crankcase assembly as in claim 1 wherein said crankcase assembly is adapted to provide a support for said engine, and wherein said crankcase assembly further comprises: mounting pads positioned adjacent opposite ends of said matched housings on the outer facing sides thereof for securing said engine to a support member; and said mounting means being symmetrical relative to said normal plane.
 5. A crankcase assembly as in claim 1 wherein said housing securing means and said cylinder mounting means further includes: passageway means extending through said housings normal to the longitudinal axis thereof and positioned so that a single passageway means extends through said casings adjacent one side of a cylinder on one casing and the other side of a cylinder on the opposite casing; and bolt means extending through said passageway means for connecting said rows of cylinders to said casings and connecting said casings to one another.
 6. A crankcase assembly as in claim 5 in combination with rows of cylinder assemblies extending from said cylinder mounting means, said cylinder assemblies having intermediate barrel portions and head portions at the outer extremities thereof, and wherein: said bolt means extends through the housings to an outer facing side of the head portion of a cylinder assembly on the opposite side of the engine axis; and whereby said housings and said cylinder barrels are secured in compression.
 7. Apparatus as in claim 6 wherein: said bolt means further comprise an expanded portion at the midpoint thereof to line up opposing passageway means through which the bolt means extends; and whereby said bolt means key said crankcase halves with one another.
 8. A crankcase as in claim 2 wherein said crankcase assembly further comprises means for providing a flow path for lubricating fluid to said journaling means, said flow path means comprising: a tube extending through openings in the plurality of ribs, said tube being positioned generally parallel to the longitudinal axis of said housings and to one side of said arcuate recesses; passageway means extending from the arcuate recess of said inner ribs through said inner ribs to the interior of said tubular member, said tubular member having apertures communicating with each of said passageway means; and said tubular member having the same coefficient of expansion as said casings for preventing leaks of the junction therebetween over substantial temperature changes. 